Inertial Measurement Unit

Keywords: Inertial Measurement Unit, IMU, motion sensors, gyroscopes, accelerometers, GPS

Planar Wireless Inertial Measurement Unit (WIMU)

Recently developed Tyndalls' planar inertial measurement unit has been designed to focus on various requirements in movement tracking and orientation estimation. The planar WIMU coupled with the 2.4GHz transceiver, RF Nordic nRF2401, produces a very powerful customisable wireless node. Alternative implementations enable the Zigbee (IEEE 802.15.4) communications in the 25mm form factor if required . Thanks to high spec motion sensors used and variability of ranges, the IMU can be used in wide range of application including sports player motion tracking (link to:projects/ongoing/Clarity) or accuracy improvement for GPS based systems. Additional external data processing or Kalman filtering can be implemented on coupled PC or attaché microcontroller/DSP board.

·          Accelerometer: ±2,4,8,16 g, 16 bits resolution, digital

·          Magnetometer: ±125 µT, ±200 µT, ±700 µT, ±4000 µT, up to 12 bits resolution, digital

·          Gyroscope: ±500 deg/s or 2000 deg/s, analog + 14 bit ADC

·          Small & robust design

·          Fully planar design with no vertically mounted components

·          25 mm Tyndall mote compatible high specification motion sensors

·          Low cost & low power

·          Storage capacity for sensor calibration values (EEPROM)

Tyndall Inertial Measurement Unit – Planar Design

25mm WIMU

The Tyndall 25mm WIMU is a 6 DOF IMU module, which is made up of an array of inertial sensors coupled with a high resolution analog to digital converter (ADC). The 25mm WIMU module utilises the wireless communication capabilities of the 25mm wireless node to realise a fully autonomous WIMU module.

·          Accelerometer: 2xADXL202, analog 

·          Magnetometer:  2xHMC1052L, analog

·          Gyroscope: 3xADXR150, analog

·          12 bit ADC

The inertial sensor array consists of three single axis gyroscopes, ADXRS150 from Analog Devices, two dual axis accelerometers, ADXL202 from Analog Devices, and two dual axis magnetometers, HMC1052L from Honeywell. The sensor array was designed with a novel 3D structure, which produces the 6 required degrees of freedom (DOF) necessary to determine position. The module also has a 12-bit ADC chip, AD7490  from Analog Devices, handling the data conversion. This chip has a Serial Peripheral Interface (SPI), which allows easy interfacing to the ATMEL microcontroller.

(link to:projects/ongoing/Clarity)

Inertial Measurement Unit orthogonal design

IMU & GPS data merging

The IMU data can be used to improve accuracy and resolution of traditional GPS systems or provide short time localization data when GPS signal is not available. Tyndall 25mm GPS mote can be link to the 25mm WIMU or planar WIMU to provide combined system where long term accuracy is given by GPS while short term improved resolution can be increased by using IMU sensor data. Both inputs can be processed using Kalman filtering technique to provide localization and orientation data with improved accuracy. Whole system can be also equipped with RF transceiver for wireless data transmission.

Tyndall Wireless Sensor GPS unit

Contact:

Jan Vcelak  - Jan.vcelak@tyndall.ie

Relevant Projects:

• SugarCube
• Multipleye

Selected Publications :

• J. Buckley, B. O'Flynn, J. Barton, S.C. O'Mathuna,“A highly miniaturized wireless inertial sensor using a novel 3D flexible circuit”, Microelectronics International, Volume 26 Issue 3, pp. 9-21 (Jul 09)

• Giuseppe Torre, Javier Torres, Mikael Fernstrom, Brendan O’Flynn, “Algorythm for Tracking Orientation Development of POINTINGAT”, Proc.NIME2008, 8th International Conference on New Interfaces for Musical Expression, 5 - 7 June 2008, Genova, Italy

• Brendan O’Flynn, J Barton, A Gonzalez, J Buckley, S C O’Mathuna, “Sugarcube WIMU – The implementation of a highly miniaturized Wireless Inertial Measurement Unit”, Proc. XXXI International Conference of IMAPS Poland Chapter Rzeszów - Krasiczyn, 23 - 26 September 2007, pp. 491-494
• Javier Torres , Brendan O'Flynn, Philip Angove, Frank Murphy and Cian O'Mathuna, “Motion Tracking Algorithms for Inertial Measurement”, Proc. BodyNets 2007 2nd International Conference on Body Area Networks, 11-13 June, 2007, Florence (Italy)
• J Barton, A Gonzalez, J Buckley, B O’Flynn, S C O’Mathuna, “Design, Fabrication and Testing of Miniaturised Wireless Inertial Measurement Units”, Proc. ECTC 2007, Reno, Nevada, USA, May 29 -June 1, 2007, pp1143-1148